1. Field of the Disclosure
The present disclosure is directed to a method of forming an electronic device, and more particularly, forming metal-semiconductor films having different thicknesses within different regions of an electronic device.
2. Description of the Related Art
Transistors, such as CMOS transistors, are created such that certain portions have low-resistivity regions. Particular low-resistivity regions can be formed for electrical contacts, and can include the formation of a metal-semiconductor film (e.g., a silicide film) typically including a process of salicidation in the case of a silicon film including a metal material. Some typical metal-semiconductor films include titanium silicide (e.g., TiSi2), nickel silicide (e.g., NiSi), and cobalt silicide (e.g., CoSi2). However, certain problems are associated with the formation of such metal-semiconductor films. For example, the metal-semiconductor film may be susceptible to certain defects, such as “mouse bites” or agglomeration, which are thought to be linked to the thickness of the metal-semiconductor film formed and the amount of silicon available within the region during the forming process.
FIGS. 1-2 illustrate a typical prior art method of forming a metal-semiconductor film. FIG. 1 includes a cross-sectional illustration of a transistor structure 103 including a gate oxide film 104, gate electrode 106, and spacers 108 and 110 formed over a substrate 102. Typically, the salicidation process is initiated by forming a cobalt film 112 over the transistor structure 103. After forming the cobalt film, the process continues as illustrated in FIG. 2 by reacting the cobalt film 112 with silicon to form metal-semiconductor film portions 122 and 124 and removing unreacted portions of the metal-semiconductor film. Such a reaction can typically include heat treatment, such as an annealing technique. The metal-semiconductor film portions 122 formed on the source and drain regions of the transistor structure 103 are generally uniform, typically having the same thickness. Moreover, metal-semiconductor film portions formed on source and drain regions of other transistor structures (not illustrated) have the same thickness as metal-semiconductor film portions 122 of transistor structure 103. Additionally, the metal-semiconductor film portion 124 formed on a portion of the gate electrode 106 will have the same thickness as other metal-semiconductor film portions formed on other gate electrodes.
While such a process facilitates the formation of a metal-semiconductor film the formation of such films may be susceptible to agglomeration, grooving, or other defects.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.